The present invention relates generally to novel implantable medical devices that include a new family of miniature antennas in the device. Also, the invention relates to several novel ways of arranging said miniature antennas inside implantable medical devices, and novel wireless communication systems comprising implantable medical devices with an integrated antenna.
Implantable medical devices (such as for instance cochlear implants, hearing devices, neuro-stimulators, cardioverter defibrillators, congestive heart failure devices, pacemakers, ventricular assist devices, artificial hearts, insulin pumps, drug pumps, incontinence devices, bone growth stimulators, or orthopedic implants) are currently used to treat a medical condition or pathology of a patient (e.g., an insulin pump to treat diabetes), or to overcome an impairment of a physiological functionality (e.g., a cochlear implant to restore the hearing functionality).
These devices have the capability of monitoring one or more physiological variables (such as for example cardiac heartbeat rate, blood glucose levels or blood pressure) by means of one or several sensors, and/or applying stimuli to the appropriate body organ or limb (such as for example an electrical discharge, or the release of a drug) by means of one or several actuators. Furthermore, in order to provide a particular functionality (for instance cardiac rhythm management, monitoring of activity levels, blood drug delivery or neuromuscular stimulation) the implanted medical device comprises an electronic circuitry that processes the collected physiological information and delivers the correct treatment.
Typically, an implantable medical device needs to be programmed to meet the specific particularities of the medical condition of a patient. Although this task can be performed initially either before or during the surgical procedure to implant the device into the recipient, the medical conditions or the body of the patient are likely to evolve over time, thus making it necessary to re-adjust the implanted device accordingly to these changes in order not to degrade the effectiveness of its therapeutic functionality.
The programming (including reprogramming) of the implanted medical device is usually done by controlling the device with an external programming unit. Therefore, it is advantageous to realize such programming and reprogramming using non-invasive techniques, like for example a radiofrequency link with a wireless implanted device, as it reduces discomfort to the patient and avoids the risk and the cost of surgery.
In some prior-art cases, a wireless implantable medical device and an external control unit use a near-field technique for the communication. According to this technique, signals are coupled inductively between an external antenna and an antenna in the implantable device, usually a coil antenna.
One of the problems of this technique is that, as the near-fields decay very rapidly with distance, the external antenna (typically a loop antenna) has to be placed within a few centimeters from the implanted device in order for the communication to take place, which is inconvenient for a clinician, reduces the mobility of the patient, and allows limited functionality between the implantable medical device and the external unit.
As an alternative, some prior-art implantable medical devices use far-field radiofrequency to communicate with an external unit. This option overcomes the problem of short range, as the communication can take place over greater distances, whereby this technique implies minimal restrictions on the physical activities in which a patient can participate, and enables the individual to remotely monitor and control a medical condition without feeling restricted by the medical device.
However, an important problem of this approach is the integration of an antenna in such small implantable devices, as the space required for an antenna to operate at the frequency bands typically used for medical applications is large compared to the dimensions of these devices.
Furthermore, attempts to make small antennas have resulted in these antennas being very inefficient, which leads to a decreased range, an increase in power consumption and, therefore, to shorter battery life.
The present invention addresses this problem as it discloses how to integrate an antenna in an implantable medical device such that the antenna size is compatible with the dimensions of the medical device, while exhibiting good electrical performance.